ANOTHER EXPERIMENT IN SECOND-YEAR COLLEGE CHEMISTRY W. R. CARM~DY, REEDCOLLEGE, PORTLAND, OREGON
Laboratory work i s rapidly becoming the step-child of our chemistry curricula, being accepted as a necessary &l, curtailed i n some instances and turned over to the uncertain care of graduate assistants i n others. This article describes a second-year chemistry course i n which the laboratory work i s ~ i v e na position of importance and i s supervised by the instructor who delivers the course lectures.
. . . . . . Introduction
A recent communication of A. H. Kunz ( I ) describing "An Experiment in Second-Year College Chemistry" suggests to the writer that an experiment which has been in progress for a decade a t Reed College might be of EDUCATION. interest to readers of the JOURNAL OF CHEMICAL The second-year course in chemistry a t Reed College, in the words of the catalog, is "Analytical Chemistry, a combined course in qualitative and quantitative methods of chemical analysis designed to develop the powers of exact observation and deduction and the attainment of methods of precision in chemical technic." I t forms the second part of a four-year unified course of instruction developed and conducted by members of the department. Preceded by a first-year course in general chemistry, a prerequisite, the second-year course is followed by a year of organic chemistry and a year of physical and theoretical chemistry for which courses it is a prerequisite. General chemistry is a course in fundafnental principles and important reactions of chemistry with emphasis given to scientific methods of experimentation, observation, and reasoning. Near the end of the year, methods of simple testing are included but no systematic qualitative analysis. With assignments and laboratory work arranged according to the preparation and ability of the student, the first-year course serves all classes, students majoring in natural science and others. However, ohly those who have demonstrated superior ability in experimentation and scientific reasoning are eligible to take the second-year course. Students successful in the second-year course and in the qualifying problem given a t the end of the year are eligible to take the organic course. Having analytical chemistry as a prerequisite, the third-year course is designed upon more precise lines than otherwise would be possible. The analytical as well as the synthetical aspects are considered in the laboratory work. Outline of Course 1. GeneralIntroduction. Discussion of standards of course, texts, references, laboratory notebooks, and laboratory and written examinations. 1244
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Ezperiment 1: Preparation of 6.0 Normal Reagents. Discussion of equivalent weights, molality, normality, calculations, and labeling bottles. Ezperiment 2: Calibration of Burets. Demonstration of cleaning, manipulation, data form, use of balance, and calculations. Precision in Analytical Chemistry. Methods of expression, types, significant figures, classification of errors, precision in quantitative methods. Volumetric Titration Methods. Classification, endpoints, indicators, errors, and precision. Experiment 3: Titration Practice. Statement, endpoints and indicators, demonstration, calculation of results, elimination of errors. Acidimetric-Alkalimetric Methods. Theory, titration curves, and choice of indicator. Experiment 4: Report on Care and Use of Platinum and Hazardous Chemicals. Experiment 5 : Calibration of Volumetric Flasks. Statement, discussion, and demonstration. Oxidation-Reduction. Valence and its change, balancing equations, reactions, effect of hydrogen-ion concentration, equivalence, normality, and molality. Experiment 6: Preparation of Primary Standard for Acidimetry. Primary standards, requirements, and preparation. Ezperiment 7: Preparation and Standardization of 0.2 Normal HC1 Solution. Demonstration. use of reference indicator and calculations. Experiment 8: Determination of Unknown Base. Laboratory Emmination No. 1: (Seventh week). Unknown Reauirine Use o f Princibles o f Acidimetry and Solutions ~ l r e a d yhandard&ed. Oxidation-Reduction Methods. Reactions, endpoints, indicators, original standards. and analvsis of ~ermaneanate,dichromate, and iodyne methods. Exberiment 9: Prebaration and Standardization o f Potassium ?ermanganate ~ o i u t i o n . Experiment 10: Preparation of Standard Potassium Dichromate Solution. Ezperiment 11: Determination of Iron i n Hematite by Permanganate and Dichromate Methods. Ezperiment 12: Volumetric Iodine Methods. Preparation and standardization of solutions of Iodine and Sodium Thiosulfate. Laboratory Examination No. 2: (Twelfth week). Unknown Requiring Use of lodimetry Methods of Analysis. Precipitation Reactions. Common-ion precipitation, generalizations, theory of titration, endpoints, indicators, original standards. Ezperiment 13: Volumetric Determination of Chlorzde and Thiocyanate. Electrometric Reactions (Taken in Physical Chemistry). Gas Reactions (Taken in Economic Chemistry).
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The Atom, Atomic Structure and Its Relation to Physical and Chemical Properties. (a) The Atomic Theory. History, foundation, and importance and methods of determining atomic weights. (b) Periodic Classification of the Elements. History, importance, and relationships. (c) Radioactivity. Rays and radiations and radioactive series. (d) Electron Theory. Structure of atom and relation t o chemical properties. Experiment 14: Calibration of Weights. Gravimetric Methods. Classification of types and demonstration of methods of precipitation, filtration, and ignition. Experiment 15: Complete Analysis of BaC& 2Hz0. Experiment 15A: Determination of Silica in-a Soluble Silicate. Electrolytic Analysis (Taken in Physical Chemistry). Chemical Reaction in Water Solution. (a) Solvents and Solubility. Classification according to anions. (b) Ionization. History, classification of acids, bases, and salts. (c) Acidity and Basicity of Hydroxides. Classification of hydroxides. (d) Complex Ions. (e) Dynamic Equilibrium and Mass Action. Historical. mathematical develo~ment,and demonstration of concentration effect. (f) Equilibrium and Mass ActionrApplied to Ionized Systems. Simple ionization, complex ions, the water equilibrium, hydrolysis, buffer solutions, regulation of ionic concentration, methods of increasing and decreasing solubility, ~ r e c i ~ i t a t i owith n hydrogen sulfide, and summary of . ionicAequilibria. Practical Qualitative Analysis According to the Procedure of A. A. Noyes (2). Noyes' method, precision of separations, and recording of results. Systematic Anion Analysis. Classification, preliminary tests, and demonstration of complete analysis. Experiments 16-25: Anion Analysis. (Noyes, Expts. 52, 35, 38, 39, 41, 44, 45, 46, 47, and 49.) Laboratory Examination No. 3: (Nineteenth week.) Unknown alkali anion. Solution of Substance for Cation Analysis. Demonstration. Experiment 26: Solution of Unknown Substance. Systematic Cation Analysis. Chemistry and analysis of cations by groups. Experiments 27-35: Noyes, Expts. 1, 3, 5 , 7 , 8 , 10,11, 12, and 13. Laboratory Examination No. 4: (Twenty-fourth week.) Unknown, Anion, and Cation of Silver. Copper, and Tin Groups.
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Experiments 36-42: Noyes, Expts. 14, 16, 17, 18, 19, 20, and 21. Laboratory Examination No. 5: (Twenty-seventh week). Unknown, Anion, and Cation of Silver, Copper-Tin, and IronAluminum Groups. Experiments 43-45: Noyes, Expts. 22, 23. and 26. Experiment 46: Unknown, Alkaline Earth Group. Experiment 47: Qualitative and Quantitative Annlysir of General Unknown. 18. Summary of Chemistry of Elements. Classification according to periodic table. Laboratory Examination No. 6: (Thirty-third week). Unknown Technical Substance (Anion and Cation). Laboratory Examination No. 7: (Thirtv-third week). Volumetric
Analys& Speed Test. Experiment 48: Laboratory Problem (Twenty-seventh to thirtythird week). Complete analysis of unknown mineral requiring exceptional skill. Students qualifying for organic chemistry elect this problem in place of experiments 46 and 47, and laboratory examinations 5, 6, and 7. Method of Instruction The lectures are designed primarily to discuss the principles involved in the laboratory work and to demonstrate the technic. About half of the 68 fifty-minute periods (two periods per week for 34 weeks) are spent in preparing the students for the laboratory, the remaining time being devoted to the principles of chemical change and reactions important in analytical chemistry. C The course as a whole follows no textbook; chapter and sometimes page references are given to the numerous books available in the departmental library. The students procure copies of "Noyes" (Z),which is used as laboratory manual for qualitative analysis, "Chapin" (3), and 'Tales" (4) to which assignment and reference are more often given. This method of assignment and reference furnishes the connecting link between the firstyear course in which a text is followed and the third-year course in which no text is used. As part of the system of instruction rather than as examinations, written tests are given a t regular intervals. These comprise exercises and problems which are designed to test the ability of the student to apply or arrange or classify what has been previously discussed. Papers are orally criticized and returned to the students for reorganization and correction. This is repeated until the paper is approved. The laboratory work is designed to be covered in 297 hours of which 198 (6 hours per week for 33 weeks) are a t specified times and are supervised by the instructor who gives the lectures. The remaining 99 hours are arranged by the student to suit his convenience. A period is set aside
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each month for a laboratory examination which is designed to test the ability of t h e student to use the principles previously studied. Eligibility to take the examination is contingent on having completed assigned work. The preparation of the student and his understanding of the principles and method is ascertained by preliminary written reports and by oral quiz before each experiment. In order to eliminate loss of time and interruption of laboratory work caused by frequent trips to the stockroom window, materials and chemicals are distributed by the instructor some time before they are to be needed or a t the time of the oral quiz, a complete set of Noyes' reagents is assembled by each student, and test solutions and special reagents are available on the side shelves of the laboratory. Discussion The design of this course in second-year college chemistry is based on a belief in the validity of two principles: (1) that a laboratory course offeringa comprehensive training in precision methods and in the principles and technic of analytical chemistry is a necessary part of a four-year chemistry curriculum; (2) that essential to efficient laboratory instruction is a thorough understanding by the students of the principles, reactions, and methods involved in each experiment before it is attempted in the laboratory. The course attempts to satisfy these principles by the methods of instruction outlined above. Direct correla&on between lecture and laboratory, laboratory examinations, preliminary oral rFports, and the elimination of unnecessary interruptions have all seemed to aid materially in accomplishing this result. Experience indicates that the direct correlation between lecture and laboratory is best obtained by having the instructor who gives the lectures personally supervise the laboratory and problem work. This may lay an unusual burden upon the lecturer whose time may be considerably monopolized by the constant supervision of a laboratory section, and might offer some difficulty in large institutions where several laboratory sections might be necessary. The writer believes, however, that the sacrifice thus entailed would be well justified and repaid by the increased efficiency possible. Literature Cited KUNZ. "An Experiment in Second-Year College Chemistry," J. CHEM.EDUC., 8, 2192-7 (Nov., 1931). A. A,, "A Course of Instruction in the Qualitative Chemical Analysis of ( 2 ) NOYES, Inorganic Substances," The Mamillan Co., New York City, 1929. ( 3 ) CHAPIN,"Second-Year College Chemistry," John Wiley & Sons, Inc., New York City, 1927. ( 4 ) FALES,"Inorganic Quantitative Analysis," The Century Co., New York City, 1925. (I)
